Enantioselective degradation of dufulin in four types of soil.

In this study, enantioselective degradation of dufulin in four types of soil (Guiyang silty loam, Nanning silty clay, Hefei silty clay, and Harbin silty clay) was investigated under sterile and nonsterile conditions. Pesticide residues in soil samples were extracted with acetonitrile. S-(+)-Dufulin and R-(-)-dufulin were separated and determined on an amylose tris(3,5-dimethylphenylcarbamate) (Chiralpak IA) chiral column by normal phase high-performance liquid chromatography (HPLC). The absolute configurations of dufulin enantiomers were determined by obtaining experimental and computed circular dichroism spectra. Dufulin enantiomers were found to be configurationally stable in the selected soils, and no interconversion was observed during the incubation of enantiopure S-(+)- or R-(-)-dufulin under nonsterile conditions. Compared to the half-life (t1/2) of dufulin in sterile soils, the degradation rate was higher in nonsterile soils, which suggests that dufulin degradation can be attributed primarily to microbial activity in soils used for agricultural cultivation. Furthermore, enantiopure S-(+)-dufulin degraded more rapidly than its antipode. This suggests that use of enantiopure S-(+)-dufulin could exert less disturbance to soil bioactivity and contribute less to environmental pollution.